Nylon bearing material



Dec. 3, 1968 w. M. LAIR ET AL NYLON BEARING MATERIAL Filed May 5, 1966OQO Om .O

NOLLOIHj IO LNBIDIi-EOD INVENTORS WILBERT M. I AIR BY JOHN s. TAYLORATTORNEY United States Patent O 3,414,516 NYLON BEARING MATERIAL WilbertM. Lair and John S. Taylor, Newark, Del., aS-

slguors to The Budd ICompany, Philadelphia, Pa., a corporation ofPennsylvania Continuation-in-part of application Ser. No. 463,565,

June 14, 1965. This application May 5, 1966, Ser.

11 Claims. (Cl. 252-12) ABSTRACT F THE DISCLOSURE A self-lubricatingbearing element having a low coefficient of friction comprising asubstantially non-porous load bearing body of nylon having substantiallyuniformly dispersed therein colloidal sized particles of a sorbent withsorbed lubricant.

This invention relates to novel bearing materials having a lowcoefficient of friction. More particularly, it concerns permanentlylubricated nylon bearings. This application is a continuation-impart ofapplication Serial No. 463,565 filed lune 14, 1965, now abandoned.

The term nylon as used in this specification and appended claims isintended to be generic to any long-chain polymeric amide which hasreoccurring amide groups -CONH- as an integral part of the main polymerchain.

Nylon possesses `a unique combination of desirable properties such ashigh strength and resistance to abrasion. Unfortunately, non-lubricatednylon has a relatively high coefficient of friction in comparison withcertain other plastics used for bearings. Thus, nylon bearingsheretofore have been used where a relatively high coefficient offriction could be tolerated or where the nylon bearings could belubricated. Lubricants substantially reduce the coefficient of frictionof nylon, but must be constantly applied to a nylon surface to maintaina low coefficient of friction. In many applications, it is eitherimpossible or impractical to constantly lubricate a nylon bearingsurface.

Permanently lubricated bearings are highly desirable. Many attempts havebeen made to provide permanently lubricated nylon bearings byincorporating oil in the nylon. One attempt consisted in forming aporous `bearing by sintering together nylon particles and filling thepores with oil.` The resultant bearing was relatively weak structurally,and the lubricant settled and bled from the bearing. Another attemptconsisted of encapsulating oil droplets in ,the nylon. Unfortunately,the oil formed into relatively large size, non-uniformly distributedpockets, which weakened the bearing.

In addition to the above-mentioned problems encountered in attempting toprovide a permanently lubricated nylon bearing, special problems wereencountered in attempting to provide such a bearing using anionicallypolymerized nylon, hereinafter referred to as A.P. nylon. A.P. nylon isproduced by polymerization of anhydrous monomeric cyclic lactams having3 to 12 carbon atoms in the nucleus of the lactam ring, such as epsiloncaprolactam, in the presence of strongly basic catalysts, for examplealkali metals such as sodium, potassium and lithium, and alkaline earthmetals, and certain derivatives of such metals, for example lithiumhydride, alkali metal alkyls, etc., at elevated temperatures in thepresence 0f a promoter. When the lubricating oil was added to themonomer, heretofore it was not possible to prevent a major portion ofthe lubricant from separating from the monomer. As the polymerizationprogresses additional quantities of oil separated. Thus, substantialamounts of a lubricant could not be satisfactorily incorporated intoA.P. nylon before the present invention.

3,414,5 16 Patented Dec. 3, 1968 "ice An object of this invention is toprovide nylon with improved anti-friction properties.

A further object of this invention is to provide a process for producingpermanently lubricated nylon.

Another object of this invention is to provide permanently lubricated,substantially non-porous nylon bearings having a low coefficient offriction and high strength.

Still another object of this invention is to provide A.P. nylon articleshaving incorporated therein a lubricant in amounts and in a form toprovide permanent lubrication.

A still further object of this invention is to provide a novel nylonbearing which is permanently lubricated to maintain a low coefficient offriction even under a relatively high dynamic load.

Another object of this invention is to provide nylon bearings havingimproved PV Values.

Other objects and advantages of this invention will become furtherapparent from the description and from the drawing which shows, in termsof coefficient of friction vs. pressure, a comparison of the permanentlylubricated nylon of the invention and non-lubricated nylon.

Briefly, the objects of this invention are obtained by combining nylon,lubricating oil, and a finely divided sorbent, the lubricant beingsorbed by the sorbent and the sorbent being uniformly dispersedthroughout the nylon.

The mechanism by which the lubricating oil is associated with thesorbent is not known exactly. For this reason the mechanism is referredto herein as sorpton, which includes the many phenomena commonlyincluded under the terms adsorption and absorption. The material withwhich the lubricant is associated is, therefore, referred to as asorbent. Tests suggest, however, that the mechanism is primarilyadsorption. It was found that when equivalent weights of carbon blackshaving different surface areas were used, the amount of oil taken up bya carbon black was proportional to its surface area, indicating that theassociation is primarily a surface-function, namely, adsorption.However, there is no intention to be limited by thisvstatement becauseof the inability to ascertain with the necessary degree of certaintyptheexact mechanism of the association between lubricant and sorbent.

Various types of nylon may be used to advantage in the presentinvention. As stated above, these materials are synthetic linearpolyamides characterized by the presence of recurring amide groups as anintegral part of the main polymer chain. They may be furthercharacterized by a high melting point and insolubility in most solvents.

Nylon suitable for use in this invention is generally one of two types,one being prepared by (l) the interaction of a diamine with at least onefree hydrogen atom attached to each amino group and a ydicarboxylicacid, and the other by (2) the condensation of amino carboxylic acids,their lactams or derivatives. The reaction products from (1) have thefollowing structural arrangement:

while those from (2) have the structural arrangement:

-CO-R--NH--CO-RwNH-CO-R-NH- (II) where R and R represent alkylene chainscontaining the same or different numbers of alkylene groups, generallytwo or more. A representative example under (l) is t-he reaction productof adipic acid and hexamethylene diamine. A representative example under(2) is the reaction product of the self polymerization of e-caprolactam.

A preferred nylon for employment in this invention is A.P. nylon, which,as stated above can be prepared by the base-catalyzed polymerization ofhigher lactams-i.e., lactams having 3 to 12 carbon atoms in the nucleusof the lactam ring. The currently most important lactum in this categoryis e-caprolactarn. Other suitable higher lactams includemethylcyclohexanone isoximes, cycloheptanone isoxime, cyclooctanoneisoxime, cyclic hexamethylene adipamide, pyrrolidone, etc.

The anionic polymerization of higher lactams is accomplished by usingvarious catalyst and promoter systems such as those disclosed in BelgiumPatent 623,840 and in U.S. Patents 3,017,391 and 3,017,392. Although theinvention is described particularly in connection with A.P. nylon formedfrom e-caprolactam, it is to be understood that the invention is notlimited to such A.P. nylon or to any particular polymerization process,but is applicable to various types of nylon.

In order to more clearly demonstrate the advantages of this inventionreference is made to the -drawing in which the ordinate represents thecoefficient of friction and the abscissa the pressure applied to thenylon test piece. Curve 1 represents the results obtained withpermanently lubricated A.P. nylon (polymerized epsilon caprolactam) madeaccording to the teachings of this invention. Curve 2 represents theresults obtained with the same non-lubricated A.P. nylon. Curve 3represents the results obtained using non-lubricatedpolyhexamethyleneadipamide (du Pont nylon 6/ 6).

The values for coefficient of friction were obtained using a thrustwasher-type tester set to give 25 ft. per minute average surface speed.The load on the test sample was increased in gradual increments. Aftereach increase, the temperature change was noted. If the temperaturereached equilibrium, the amount of loading was then further increased. Afailure was noted when the temperature did not reach equilibrium andcontinued to rise until it approached the melting point of the nylon.

Under the test conditions the non-lubricated A.P. nylon (polymerizede-caprolactam) and non-lubricated polyhexamethyleneadipamide exhibitedcoefficients of friction higher than that obtained with the permanentlylubricated nylon of this invention. Of even greater importance, asloading was increased, the non-lubricated nylons failed but thecomposition of this invention did not fail even at pressures four timesgreater than failure pressures of the non-lubricated nylons. Morespecifically, the non-lubricated nylons failed when pressures between 37and 47 p.s.i. were applied. The novel permanently lubricated A P. nylonof this invention did not show any signs of failure when pressures inexcess of 190 p.s.i. were applied. The coefficients of friction of thenon-lubricated nylons at 37 p.s.i. were 0.40` and 0.325, respectively.The permanently lubricated nylon of this invention `exhibited acoefficient of friction of only 0.116 at 37 p.s.i. At the greatlyincreased loading of 192 p.s.i., where it is impossible to use theaforementioned non-lubricated nylons, the novel permanently lubricatednylon exhibited a coefficient of friction of only 0.067.

A further advantage of the novel nylon composition of this invention isits capability for supporting high dynamic loads while maintaining arelatively low coefficient of friction.

Lubricants suitable for use in this invention are well known. Theprimary function of the lubricant is to lower the coeicient of frictionbetween the nylon and the object in sliding contact with the nylon.Accordingly, the lubricant must be suitable for the particular speedsand pressures under which the bearing is to operate. An importantproperty affecting lubricity is viscosity. In the permanently lubricatednylon bearings of this invention, lubricants have a viscosity of betweenabout 10 and 700 centistokes at 100 F. have been found to beparticularly satisfactory.

The manner of adding the lubricant and solvent to the nylon will bedescribed in detail hereinafter, but at this time it may be noted thatin one embodiment the oil and sorbent are added to molten nylon and inanother embodiment the oil and sorbent are added to a monomer which issubsequently polymerized to a nylon. Accordingly, the oil must beresistant to thermal degradation and be nonvolatile at the melttemperature of the nylon or the poly-merization temperature of themonomer, as the case may be. The melt temperature is determined in themanufacture of the nylon and will vary according to the specificationsfor the particular grade of nylon. The lubricant should not vaporize atthe melt temperature or polymerization temperature for t-he gas producedon volatililzation occupies considerably more volume than the uid, andupon condensation of the lubricant when the temperature is reduced,voids will lform in the nylon.

An additional factor to be considered is the relative reactivity of thelubricant with the nylon or monomer. The.l oil will be in contact withthe nylon or monomer at elevated temperatures and therefore the use oflubricants reactive with the nylon or monomer should be avoided. In thisconnection, in the A P. nylon process lubricants containing active (-OH)groups may react with the catalyst and impair the formation of thepolymer, and their use is, therefore, not recommended in such process.

The lubricant can be selected from both natural and syntheticlubricating oils and waxes. The preferred natural lubricants foremployment in this invention are the hydrocarbon oils and waxesparticularly those having a molecular weight from about 200 to about1000 and `about 15 to about carbon atoms in their molecular structure.Such hydrocarbons may be straight chain, branched chain, or cyclic instructure. The preferred hydrocarbon lubricants are the straight andbranched chain paraflins having a molecular weight of from about 280 to.about 700. These hydrocarbon oils are preferred for most applicationsbecause of their relatively low cost, good lubricity and resistance todegradation.

Certain of the synthetic lubricants are highly desirable for use inspecial applications. These lubricants must meet the requirements notedabove; namely, lubricity, resistance to thermal degradation, andnon-volatility and non-reactivity with nylon or monomer at processingtemperatures. The high molecular weight polyalkylene glycols made by thereaction of `an alcohol with polymerized ethylene and propylene glycol,the synthetic esters of primary alcohols and dibasic acids, such asadipic and sebacic acid, and organic esters of phosphoric and silicicacid have been found useful .and are relatively inexpensive. Two groupsof special utility are the silicone oils and the halogenatedhydrocarbons. Silicone oils which are linear and cyclic polymers of theformula (-SiR2O-)n exhibit excellent thermal properties. The halogenatedhydrocarbons include both the chlorinated and fluorinated hydrocarbonsland exhibit excellent lubricity and stability, the fluorocarbon oilsbeing extremely stable.

The sorbent can be any one of a considerable number of materials. Thesorbent should possess certain properties such as the ability toassociate with relatively large amounts of liquid lubricant to preventthe lubricant from forming into pockets. It should be resistant tothermal de-gradation at polymerization temperatures or the melttemperaure of the nylon. Materials which have been found to beparticularly suitable for use in this invention are carbon black,silica, and silicates, such as clays of the kaolin type. A particularlyuseful sorbent comprises a mixture of carbon black and silica.

The sorbent should be finely divided and preferably should have aparticle size which is essentially colloidal, i.e., from about 1 ma toabout 1n, so that it can be dispersed uniformly throughout the nylon andwill associate with relatively large amounts of liquid lubricant.Preferably, the sorbent should have a surface area of from about 20 toabout 1200 m.2/g.; Ia surface area `of from about 100 to about 400m.2/g. being particularly preferred (Brunauer-Emmett-Teller method).

A preferred sorbent for utilization in this invention is a carbon blackwhich is alkaline or neutral, and which has a particle size and surfacearea as specified above. In addition, the carbon black preferably shouldhave the ability to sorb from about to about 375 g. of oil per l00 g. ofcarbon black according to the Standard Rub-Out Method for determiningoil absorption as described on page 289 of Physical and ChemicalExamination of Paints-Varnishes-Lacquers-Colors, by Henry A. Gardner andG. G. Sward, 11th ed., January 1960 (also adopted by the AmericanSociety for Testing Materials, Designation D332-31T). Preferably, thecarbon black should have the ability to sorb from about 50 to about 250g. oil per 100 g. of carbon black.

The amounts of nylon, lubricant and sorbent in the permanentlylubricated nylon can 'be varied considerably. The most important ratiois that of sorbent to lubricant since it is the sorbent which associateswith the lubricant and prevents the formation of large oil pockets. Theratio of sorbent to lubricant is dependent on the particular sorbent andlubricant employed. Some sorbents are capable of combining with greaterquantities of lubricant than others, therefore less is required. Withsorbents of the type described above it has been found that the weightratio of sorbent to lubricant may be in the range between about 1:10 to5:1, the preferred ratio being from about 1:5 to 1.5 :1.

The ratio of sorbent and lubricant to nylon `can be varied, and in mostinstances the end use of the bearing will determine how much oil andsorbent should be used. A ratio of from about 1 to about 35 parts byweight of the lubricating oil, and about 0.2 to about 50 parts of thesorbent, per 100 parts by weight of nylon has been found to providebearing compositions suitable for most .applications. Preferably, thepermanently lubricated nylon of this invention comprises from about 3 toabout 20 parts by weight of lubricant and sorbent per 100 parts nylon.The above proportions are especially suitable for use with A.P. nyloncomprising polymerized epsilon caprolactam, carbon black sorbent, andhydrocarbon oil lubricant.

There are many ways in which the lubricant and sorbent can be combinedwith the nylon, different preferred techniques being used for addinglubricant to nylon and for adding lubricant to the monomer. When usingnylon, the preferred technique is to initially combine the sorbent andthe lubricant in a mixer capable of grinding the sorbent to form asmooth uniform homogenous mixture. If the lubricant is a wax, it shouldbe heated to the liquid state. This mixture is then added to the moltennylon and the combination thoroughly blended. The mixture of thesorbent, lubricant and nylon is then cooled below the solidifiicationtemperature of the nylon. With nylon, this technique is preferred inthat it is possible to prepare relatively large amounts of the sorbentand lubricant mixture beforehand, thereby providing quick cycling One ofthe main advantages of the in situ anionically polymerized nylon processis that relatively large parts can be cast in place free of internalstresses and polymerized to a very high molecular weight. The freedomfrom internal stresses is ydue to the polymerization of the monomer inthe desired configuration.

In the A P. nylon process, it is essential that the lubricant beincorporated before the monomer is completely polymerized. Thepolymerization procedure usually involves mixing two batches of moltenmonomer, one containing the catalyst, which preferably has had time toreact with the monomer, and the other containing the promoter. Thesorbent and lubricant can -be added to one or both of these moltenmonomer batches either prior to or subsequent to addition of catalystand promoter. Preferably, catalyst is added to monomer subsequent toaddition thereto of the oil and sorbent. The oil and sorbent can bemixed together prior to addition to the molten monomer, or mixed in thepresence of the monomer. The addition of the sorbent somewhat thickensthe mixture from about l to about 20 parts r of the nylon materials inthe molds.

and maintains a relatively uniform dispersion of the lubricantthroughout the unpolymerized material, holding it there during thepolymerization process.

The followingexamples are illustrative of this invention; however, theinvention should not be considered to be limited to the exact proceduresshown in these examples.

EXAMPLE I 300 g. of a carbon black having an average particle size of 20ma, a surface area of 140 m.2/ g., and an oil absorption of 134 g./100g. was dried at 200 C. over night and added hot to 3000 g. of moltene-caprolactam monomer in a steam-jacketed colloi'd mill. 300 g. of aparaffin oil having a molecular weight of approximately 175 and aviscosity of 350 S.U. seconds at 23 C., and 15 g. of sodium stearatowere also added to the molten monomer and the mixture milled for 10minutes.

3.6 g. of lithium hydride was added to the resulting monomer suspensionand the mixture heated for 3 hours at 99 C. to form a lactam-base salt.

A similar quantity of a second monomer suspension having the samecomposition as that described above (prior to LiH addition) was preparedas stated and heated to 100 C., and 15 g. of triphenoxytriazine wasadded thereto.

The monomer suspension containing catlyst, heated to 88 C., and an equalquantity of the monomer suspension containing promoter, heated to 171 C.were pumped into a 3" diameter tube mold heated to about 168 C. The tubemold was rotated at 800 r.p.m. for 1 hour to form and polymerize thetube.

No residual oil Was visible on the resulting polyamide tube, and thetube had a smooth I.D.

EXAMPLE II The. procedure of Example I was repeated with the exceptionthat polymerization was carried out While the tube mold was rotated atr.p.m. rather than 800 r.p.m.

The cured polyamide tube had a smooth I.D. and the surface was free ofresidual oil.

EXAMPLE III The procedure of Example I was repeated with the exceptionthat the parain oil was rst added to the hot carbon black and theresultant sticky powder was kept overnight under a blanket of nitrogen.The sticky powder was then added to the molten e-caprolactam monomer.

The cured polyamide tube had a smooth I.D. and the surface was free ofresidual oil.

EXAMPLE 1V The procedure of Example I was repeated with the exceptionthat 210 g. of carbon black was used in each monomer suspension. Asmooth-surfaced tube free of surface residual oil was obtained.

EXAMPLE V The procedure of Example I was repeated using a carbon blackhaving an average particle size of mu, a surface area of Z7 m/ g., andan oil absorption of 70 g./100 g. A smooth-surfaced tube free of surfaceresidual oil was obtained.

EXAMPLE VI The procedure of Example I was repeated using a carbon blackcomprising colloidal size particles having a surface area of 445 m..2/g. and an oil absorption of ,gn/100 g. The polyamide tube obtained wassmooth-surfaced and free of surface residual oil.

EXAMPLE VII A smooth-surfaced polyamide tube free of surface residualoil was obtained using the procedure of Example I, with the exceptionthat the carbon black had an average particle size of 18 ma, a surfacearea of 190 m.2/ g. and -an oil absorption of 22S-250 g./100 g., and theoil comprised a paratlin oil having a molecular weight of 145 and aviscosity of approximately 125 S.U. seconds at 23 C.

EXAMPLE VIII The procedure of Example I was repeated using a carbonblack having an average particle size of 18 mit, a surface area of 190rr1.2/g. and an oil absorption of 225-250 g./ 100 g., and a paraflin oilhaving a molecular weight of about 200 and a viscosity of 500 S.U.seconds at 38 C. The polyamide tube obtained was smooth-surfaced andfree of surface residual oil.

EXAMPLE IX Using a Gifford-Wood steam jacketed colloid mill, thefollowing mix was prepared.

(1) 1000 gms. of caprolactam monomer containing 3.4 g.triphenoxytriazine promoter (2) 167 gms. of paraiiin oil (M.W. 175;vise. 350 S.U.

`seconds at 23 C.)

(3) 7 gms. of dried sodium stearate (4) 40 gms. of high structurefurnace blackl dried at 200 C.

The oil was first emulsied in the monomer and then the carbon black wasadded to give a somewhat thickened, homogeneous mixture. 660 cc. of this`mixture were then added to 220 g. of more monomer containing 0.53 g.lithium hydride catalyst. The two iluids were then mixed, forced into asheet mold and cured in the conventional manner. The surfaces of thesheet were smooth and free of residual oil.

Because the lubricant is sorbed by the sorbent and the sorbent dispersedthrough the nylon it is possible, according to this invention, to makestrong, solid, substantially non-porous bearings. The lubricant cannotbe removed from the bearing even by solvent extraction and it is almostimpossible to detect the presence of the lubricant except by measuringthe coeiicient of friction. Furthermore, the addition of a lubricantpermits the nylon to be machined by conventional means at relativelyhigh speeds as opposed to non-lubricated nylons which melt and foulcutting and shaping tools.

Blowing agents can be used to provide the permanently lubricated nylonof this invention with a porous, lightweight structure.

The following examples illustrate the improved PV Values provided by thenovel permanently lubricated nylon bearings of this invention.

PV Values are computed for bearing materials to determine their failurepoint. P is the load on the bearing surface in pounds per square inch. Vis the surface velocity of the test specimen in feet per minute. PVValues can be derived by increasing the velocity V at constant pressureP, by increasing the pressure P at constant velocity V, or by increasingboth. Failure of the bearing material is evidenced by a rapid increasein temperature of the test specimen (no equilibrium), by rapid wearand/or fiaking-otf of the surface of the test specimen accompanied byconsiderable noise.

In the following examples the test specimen comprised a thrust washer /8in diameter and 1/16" thick, having an annular flange extending aboutthe outer periphery g" wiide land extending 1A6 above the surface of thewasher. The upper flat surface of this flange having an area of 0.555in?, comprised the lbearing surface.

At each speed the loading on t-he test specimen was increased stepwiseuntil both the coetcient of friction and the temperature continued torise without an equilibrium plateau having been established. The productof the surface speed and the next lower test pressure at lAv. particlesize 18 my.; surface area 190 mP/g.; oil absorption 225-250 g./100 g,

which equilibrium was established were used in determining the PV Valueof the material tested.

EXAMPLE X Lubricated nylon bearing material having the composition ofExample I was cast into the form of a flat sheet 10 x 10 x 1/2, and atest specimen comprising a a thrust washer having the configuration anddimensions set forth above was cut from this sheet. The PV Value forthis material was determined to be 4500.

When the same non-lubricated nylon was subjected to the same test a PVValue of only 850 was obtained. A similarly low PV Value was obtainedfor another nonlubricated nylon, namely, nylon 6 (PV Value 500).

EXAMPLE XI The lubricated nylon composition of Example V was cast in theform of a rod 3 in diameter and 6 in length. A test specimen comprisinga thrust washer of the conguration and dimensions described above wasdetermined to have a PV Value of 5500.

EXAMPLE XII The PV Value of the lubricated nylon composition of ExampleVI was determined to be 6000.

It is to be understood that the form of the invention herein describedis to be taken as preferred. Various changes may be made in thecompositions and methods disclosed without departing from the scope ofthis invention.

We claim:

1. A substantially non-porous nylon load bearing body comprising fromabout l to about parts by Weight of a lubricant selected from the groupconsisting of mineral oils, synthetic oils, mineral waxes, and syntheticwaxes and from about 0.2 to about parts by weight of colloidal sizedparticles of a sorbent per parts by weight of nylon, the weight ratio ofsorbent to lubricant being in the range between about 1:10 and about5:1, said lubricant being sorbed by said sorbent, and said sorbent beingsubstantially uniformly dispersed throughout said nylon.

2. The bearing element of said claim 1 in which the nylon is anionicallypolymerized epsilon caprolactam.

3. The bearing element of claim 2. in which the fluid lubricant isparain oil.

4. The bearing element of claim 3 in which the sorbent material iscarbon black capable of sorbing from about 20 to about 375 g. oil per100 g. carbon black.

5. A substantially non-porous nylon load-bearing body comprising fromabout 3 to about 20 parts by weight of a mineral lubricating oil, andfrom about 1 to about 20 parts by weight of colloidal size particles ofa sorbent per 100 parts by weight of nylon, the weight ratio of sorbentto lubricant being in the range between about 1:5 and about 1.5:1, saidlubricating oil being sorbed by said sorbent and said sorbent particlesbeing substantially uniformly dispersed throughout said body.

6. A load-bearing body according to claim 5 wherein said lubricating oilcomprises a paran oil having a molecular weight of from about 280 toabout 700 and a viscosity of from about 10 to about 700 centistokes at100 F.

7. A load-bearing body according to claim 5 wherein said sorbentcomprises carbon black capable of sorbing from about 50 to about 250 g.oil per 100 g. carbon black.

8. The bearing element according to claim 1 in which said sorbentcomprises silica.

9. The bearing element according to claim 1 in which said sorbentcomprises a mixture of carbon black and silica.

10. The load-bearing body according to claim 5 in which said sorbentcomprises silica.

11. The load-bearing body according to claim 5 in bon black.

References Cited UNITED STATES PATENTS Beckmann 252-12.6 Austin 252-12Stott et al. 252-12 Stott 252-12 10 Mottus et al. 260-78 Butler et al.260-78 Stott 252-12 Battista 252-12.2 Schaeffer 252-12 DANIEL E. WYMAN,Primary Examiner. I. VAUGHN, Assistant Examiner.

